~ Building Information Model eXtended Markup Language
The open standard IFC holds agreements on the description of building data. IFC is very extensive and complex. This is not a problem for users, but it is challenging for software suppliers to support the full IFC standard. BIMXML was developed because in a lot of cases (between varying software) there is no need to exchange so much detail.
BIMXML is a simplified representation of a building model. Agreements have been made about spaces, buildings, floors and installations (and their properties). The geometry of BIMXML objects is simple and consists only of rectangles (extruded 2D surfaces).
BIMXML can therefore be seen as a highly simplified form of IFC. This has both advantages and disadvantages.
It is no formal open standard because it is managed by commercial software suppliers and the participation procedure on the standard is rather obscure. The most important criticism on the initiative is that it does not offer any added value for users, over the already established standard IFC.